Tractor-trailer brake system



Jan. 1, 1952 J. G. INGRES ETAL TRACTOR-TRAILER BRAKE SYSTEM 3 Sheets-Sheet l Filed May lO, 1948 flu QI Jan. 1, 1952 J. GINGRES HAL 2,581,1 07'1 TRACTOR-TRAILER BRAKE: SYSTEM Filed May l0, 1948 3 Sheets-Sheet/ Illlll'@ /w llu W f Naw Patented Jan. 1, 1952 TRACTOR-TRAILER BRAKE SYSTEM Jeannot G. Ingres and Edward G. Hill, Richmond, Va.

Application May 10, 1948, Serial No. 26,194

This invention relates to tractor-trailer brake systems, and isan improvement over the construction disclosed and claimed in the application of Jeannot G. Ingres, Serial No. 2,511,l led January 15, 1948, now sued March 8, 1951.

. It has been the common practice for a number of years to provide booster brake mechanisms for tractors and to provide on the trailer a poweroperated brake system including diierential fluid pressure operated motors responsive to energization of the tractor booster so as to apply th trailer brakes to an extent proportional to application of the tractor brakes.k Such application of the trailer brakes is conventional, as stated, and oiiers no substantial problems in the controlling of the motors of the trailer brakes. This is accomplished through the use of a relay valve mechanism commonly referred to as a conversion valve. Such valve mechanism normally connects the trailer brake motors to the atmosphere to air-suspend them, and upon energize.- tion of the tractor booster mechanism, the relay valve mechanism disconnects the trailer brake motors from the atmosphere and connects them to a source of pressure differential, usually vacuum. The relay valve mechanism includes pressure regulating means through which energiza- .tion of the trailer brake motors takes place to an extent proportional to energization of thetractor booster mechanism.

The serious defect in prior mechanisms of this type lies in the fact that the trailer brake motors cannot be energized simultaneously with the tractor booster mechanism.

frequently over 30 feet in length, and a substantial time lag is involved in the passage of air through the control line so as to actuate the relay mechanism. A further serious time lag in vacnum-operated trailer brake motors occurs because of the substantial volumes of air which must be exhausted from the variableV pressure chambers of the latter become operative.

In prior systems, it has been the practice to provide a so-called hand valve operative by the driver independently of the brake pedal for dumping air into the relay mechanism to actuate the latter and thus energize the trailer brake motors independently of actuation of the tractor booster mechanism. 'I'his has been necessary in order to insure the operation of the trailer brakes ahead of the tractor brakes to prevent jack- Patent No. 2,569,610, is- 1 trailer brake motors before the 11 Claims., (Cl. 18S-f3) knifing. The hand valve permits the driver not only to insure earlier operation of the trailer brakes, but also enables him to use the trailer brakes when a. mere brake snubbing operation is desired.

An important object of the present invention is to provide an improved tractor-trailer brake system wherein the time lag involved in the operation of the trailer brakes is eliminated through the provision of auxiliary motor means for initially applying the trailer brakes, thus permitting operation of the usual trailer brake motors after a time interval and without delaying the application of the trailer brakes. L

A further object is to provide .such a construction wherein the auxiliary trailer brake motor is instantly operative at. any time wholly independently of the booster mechanism, without even delaying the trailer brake applications by the time lags involvedY in operation of the hand valves, thus assuring the driver of complete and instantaneous control over the trailer brakes.

A further object is to provide a tractor-trailer brake system wherein a single auxiliary trailer brake motor not only provides for vinstantaneous application of the vtrailer brakes when desired, but also operates the pressure-responsive element of the regular trailer brake motors to pump air therefrom andY thus 'eliminate 'the later time lag required for the exhausting of air from the regular trailer brake motors upon actuation of the relay mechanism yincident to an operation of the booster mechanism. f

A further object is to provide a single auxiliary trailer brake operating motor which hasnovel mechanical connection with the regular trailer brake motors to mechanically operate the latter regardless of pressure conditions therein, to initially apply the trailer brakes and to displace from the regular trailer brake motors ksubstantially all of the air whichmust be exhausted therefrom upon operation of the relay mechanism in order to initiate normal operation of the regular trailer brake motors.

Other objects and advantages in the invention will become apparent during the course of the following description. l I

' Inl the drawings we have shown one embodiment of the invention. In this showing Figure 1 is a combined structural, schematic and diagrammatic view of the e tire tractor-trailer brake system. y

Figure 2 is an enlarged side elevation, somewhat'fragmentary, showing the trailer-carried portions 'of the mechanism, one of the main trailer brake motors and associated elements and the auxiliary motor control valve being shown in section.

Figure 3 is an enlarged substantially rear elevation of the trailer brake motor installation and associated elements, parts being broken away; and

Figure 4 is a horizontal sectional view on line 4-4 of Figure 3. x

Referring to Figure v1, the numeral I 'designates a conventional hydraulic brake master cylinder having the usual fluid-displacing piston (not shown) operable by a rod lII connected to the lower arm I2 of a conventional brake pedal I3. Fluid displaced from the master cylinder passes therefrom through a pipe I4 for actuating a booster mechanism indicated as a 4.whole by the numeral I5.

The booster mechanism may be of any desired type, but is preferably of the type disclosed in the prior patent to Rudolph J. Klimkiewicz, No. 2,377,699, granted June .5, 1945. .Such valoooster mechanism comprises a `differential uid pressure motor I8 formed `of opposite casing sections I9 and 20 between which is arranged a pressure operable unit comprising a flexible diaphragm 2l. This diaphragm defines with 'the casing sec tions a constant pressure chamber 22 and a variable pressure chamber 23 which, in accordance with the disclosure of the Klimkiewicz patent referred to, are normally in communication with each other. The chamber 22 communicates with a pipe A25, tapped into a pipe 2.6, one end of which leads to the intake manifold 21 of the tractor engine. The chambers 22 and 23 being normally in communication with each other, it will be vapparent that the motor I8 is .of the vacuum suspended type. Such type booster motor is'preerred in connection with the present invention.

The booster mechanism I further comprises a low pressure cylinder A3i) .and va high 'pressure cylinder 3I.` 'The .pipe .I4 communicates with the interior of the low vpressure cylinder 3.0 to operate the piston (not shown) therein to assist in displacing fluid from the high pressure .cylinder 3l and to operate the usual valve mechanism to disconnect the chambers22 and 23% from each other and to connect the mosphere. In `this connection, it will be ynoted that the booster 'motor I8 is .provided with Aan air intake .3.2 preferably Vprovided with la conventional air cleaner (not shown) and adaptedto supply air to the chamber 23 in accordance with the operation of the booster control valve Amechanism, as disclosed in the Klimkiewicz patent referred to. High pressure hydraulic fluid :is conveyed from the high pressure cylinder 3l through suitable pipe connections 33 tothe brake cylinders 34 of the tractor, ',two of these cylinders being shown in Figure 1.

4A portion of the apparatus to be described later is electrically controlled, and to this'endga switch mechanism` is provided to -be operated by Vthe driver. This switch may be controlled any suitable manner, for example by a left'foot pedal as disclosed in the pending application of Jeannot G. Ingres, Serial No. 2511, referred to above, or it may be controlled by the conventional brake pedal, las disclosed in the copending `application of Jeannot G. Ingres, Serial No.. 656,363, filed March 22, 1946, now Patent No. 2,521,835, issued October 16, 1951. In the present instance, 1-the switch mechanism is shown as being :controlled by the brake pedal. A .link 38 is connected lebetween the depending arm I2 of the brake .pedal chamber 23 to the at `tional engagement and a depending arm 39 carried by a disc 4D r'otatable on a shaft 4I, This shaft carries a switch operating arm 42 frictionally engaging the disc Il and cut away as at 43 to provide a notch, the ends of which are engageable with a pin 44 carried by the disc 49. It will be apparent that upon depression of the brake pedal I3, the disc will be rotated in a counterclockwise direction, in which case the pin 154 will tend to 4move away from its associated end of 'thenotch 43 in the position of the parts shown in Figure l. Fricof the arm 42 with the disc V4I), fhowever, will operate the arm 42 through its limit of movement as described below, whereupon the arm 'Il-2 will have its movement arrested while `the disc 40 can continue to rotate in frictional .engagementtherewith through the remainder of the range of movement of the brake pedal I3.

The Varm 42 has its upward movement limited by a pin 48, and when the arm moves downwardly -incident to .operation of thebrake pedal I3,- move lment is transmitted through a switch-operating arm 49 to a switch 250 to move it into engagement with a contact 5I. The Vswitch 159 vis connected to one ,terminal of a source 52, usuallythe vehicle battery, and the other terminal of this source is .grounded as at 5.3. The Vcontact 5I is connected-to oneendof a wire 54 leading rearwardly to the trailer Ifor a purpose to be de'- scribed.

All of the parts thus far described are carried by the tractor, as will be clear from an examination of Figure 1, :the tractor and trailer parts of the system being indicated by suitable legends at the top of the .fiigure 'Ihe variable pressure chamber 23 4of the booster motor is connected to one end of a pipe 55 which also .extendsrearwardly Yto the trailer, .the vacuum pipe l26, Vcontrol pipe 55 and single wire-54 being the only elements which Vextend vfrom the tractor to the trailer.

In the use of the present system, two vacuum tanks 8! and '6I are .preferably mounted on the trailer, 'this being done for the purpose of providing vacuum sources having different degrees of vacuum therein for a 'purpose to be described. The pipe 26 extends rearwardly to A`the trailer, as stated, and is provided with a Lnormally open check valve 62. The valve 52 can be closed under normal conditions, 'but yit is preferred that it remain normally opento reduce friction incident to the passage of a-ir therethrough in lexhausting air from the reservoirs B and 5I in the manner referred to below.

A branch pipe '63 connects the pipe 26 to the reservoirA t0. This reservoir is in open unrestricted 'communication with the pipe V2li l and the 'vacuum developed in .the reservoir 6 9 will be .the maximum degree as determinedby vacuum in intake manflold'l. While .the valve 52 is normally open, `any Vbreak in the line .to the left of this valveas viewed in Figure l will result in the immediate clo'sing .of the valve, thus preventing any increase in .pressure .in the system because of such break. The pipe 26 extends rearwardly as viewed in Figure l ,forconnectionwith .the reser voir El through-the medium of a pressure control valve 64. Such valve is employed for determining the .maximum degree of vacuum in the reservoir 51|, and thevacuum in this tank willbe substantially less than that maintained in the tank 6B for Ja purpose which will become apparent.

A relay valve mechanism indicated as a whole by the' numeral 10 is associated with the vacuum tank 60. This relay valve mechanism, commonly referred to'as a conversion valve, is conventional and need not be illustrated in detail. In common with conventional valve mechanisms of this type, the mechanism 10 is employed-for con trolling the energization of trailer brake motors in accordance with the degree of energization of the tractor brake booster mechanism. The relay mechanism 10 is connected by a pipe 1| to the vacuum reservoir 60, and the pipe 55 is also connected to the valve mechanism 10. A trailer brake motor control connection 12 is associated with the relay mechanism 10. Normally the latter mechanism connects the member 12 to the atmosphere, and upon a rise in pressure in the pipe 55 incident to energization of the -booster motor 8, the relay mechanism 10 functions to disconnect the member 12 from the atmosphere and connect it to the pipe 1|, the degree of such connection depending upon the pressure in the pipe 55 in accordance with conventional practice. Two pipes are connected to the connection 12, one for each of the trailer brake motors. One of these pipes is shown in each of Figures 1 and 2, and is indicated by the numeral 13.

Two main trailer brake operating motors are employed in the present embodiment of the invention and these motors are generally indicated as a whole by the numeral 15. 'I'he two motors are shown in Figure 3 in relationship with associated parts of the apparatus, and one of the motors is shown in section in Figure 2 to which reference is now made. Each motor 15 comprises upper and lowercasing sections 16 and 11 having peripheral edge portions clamped about the periphery of a diaphragm 18 which constitutes the pressure-responsive elementof the motor. This diaphragm has its central portion clamped `between plates 19 and 80, the latter of which seats on an annular flange 8| carried-by a powertransmitting stem 82. A nut 83 onthe upper end of this stem clamps against the plate 19. The lower end of each stem 82 is pivotally connected as at 85 to a crank arm 86 carried by brake operating shaft 81. This shaft is rotatably supported by brackets 88 carried by the axle 89 or any other structural element of the trailer by means of clamps 90 and 9| bolted tog-ether as at 92. The clamp 90 may be an integral part of the bracket 88. As show in Figure 4, one of the shafts 81 is associated with each crank 86, and one of these cranks is provided for each trailer brake motor 15.

Each motor 15 is divided by its diaphragm 18v to form a variable pressure chamber 95 and an atmospheric chamber 96. The chamber 96 com-` municateswith the atmosphere through an opening 91 in the casing section 11, this opening also extending through a bracket 98 welded or otherwise Secured to the casing 11 and preferably formed integral with the clamp 9| to support the motor 15 in position'.

The chamber 95 communicates through-a nipple 99 with a T |00, the branch of which'communicates with one of the pipes 13. These pipes conveniently may be made of rubber hose stock so as to facilitate their connection to the parts with which they are associated. The run of the T is connected through a nipple 0| with a check valve |02 having a ball check |03 therein engageable with a seat |04. A cap acts as a seat for a compression spring |06 whichnormally holds the ball |03 on its seat. The cap. |05 prei# erablyV .communicates with. the atmosphere lthrough an elbow |01 to prevent foreign material from falling by gravity into the check valve.

As previously stated the rod 82 of each motor 15 is pivotally connected as at 85 to one of the cranks 86. The pivot 85 extends through a yoke V| l0 carried by each rod 82 and above each yoke is arranged avcollar having a hemispherical lower face engageable in a similarly shaped .recess ||2 formed in a plate ||3 carried by each end vof a whiille-tree ||4. It will become apparent that the rods 82 are simultaneously operative, and accordingly the whiille tree travels bodily with these rods. The hemispherical engaging `faces of the collars and recesses ||2 are to permit a slight rocking Yof the whiille tree ||4 as may be necessary tocompensate for inequalities in the movements of the rods 82.

An auxiliary'trailer brake motor indicated as a whole by the numeral |20 is associated with the motors 15, usually in the relationship shown in Figure 3. The motor |20 may be identical with the motors 15, and may comprise upper and lower casing sections |2| and |22 having peripheral anges clamped against the opposite sides of the peripheral portion of a diaphragm |23. The diaphragmiorms with the casing sections |2| and |22 a Variable pressure chamber |24 and a constant pressure chamber |25 in xed communication with the atmosphere through an opening |26 formed in the bottom of the casing section |22. The diaphragm |23 is provided with an axial rod |21 connected thereto, and this connection may be identical with the arrangement shown in Figure 2 for connecting each rod 82 to its associated diaphragm 18.- The lower end of the rod |21 carries a yoke |28 straddling and pivotally connected to the whiiile tree ||4 as at |29.

In customary installations, the motors 15 are arranged too close together to permit the placing ofthe auxiliary motor |20 therebetween. For this reason this motor is usually arranged above the motors 15 as shown in Figure 3. For the purpose of supporting the auxiliary motor in such position, a supporting bracket |32, similar to the brackets 98 and supported in the same manner, has fixed thereto the lower ends of parallel supporting posts |33, the upper ends of which carry flanges |34 xed to the bottom of the casing section |22 in any desired manner. The bracketv |32 is provided with a relatively large `opening |35 through which the rod |21 passes, this opening and the exibility of the diaphragm |23 permitting the Whife-tree to partake of slight swinging movement incident to the swinging of the cranks 86 about the common axis of the shafts 81,A The pivot pins 85, of course, partake of the same limited swinging movement and this is permitted by the relatively large openings 91 and through the iexibility of the diaphragms 1B of the two motors The upper casing section |2| of the auxiliary motor 20 communicates through a nipple |40 with the lower end of a flexible hose |4|, and this hose leads to an auxiliary motor control valve mechanism indicated as a whole by the numeral |42. This mechanism comprises a preferably cast body |43 having a substantially central chamber |44 provided at opposite -sides with valve seats |45 and |46. A passage |41 leading from the chamber |44 is in xed communication with the vacuum reservoir 6|; The chamber |44 is also adapted to communicate with the atmosphere passage |48, preferably provided with a conventional air cleaner |49 (Figure 1). .,.Avalve kelement |,49, .ln the form of adisc, is

chemo? arranged '.inethe ehamber 1.| 44 and is rubber covered as .at |51) 'to provide resilient val-ve .iacngs engageable with .these-ats |45 and 7| 4.6. .The valve facing V`Hill 4accordingly :determines whether the chamber fl'llfltis connected `to v.the vacuum reservoir 6t| .or to 'thefatmosphere npassage |5| cornmunicates with the .chamber |44 and is connected by .a nipple a| 52 `to 1.the upper end of the pipe |'4|.

The valve disc |"49is connected zto a stem |55 carried by 'the armature 456 `of a solenoid .1| 5l arranged in ra :housing |56. Asuitably secured to the valve 'body :1143. .Aiight compression spring |59 urgesithe armature |55 toward 'the right as viewed in Figure `2 totend to maintain :the valve |49 on `theseat M5. Thus the pipe 14| 4and the variable pressure chamber I 24 fof the auxiliary :motor @are normally connected to the atmosphere. The Wire 54 is :connected to one 4terminal or the Asolenoid |51 and the other terminal of Ythis solenoid .is grounded asiat |168.

Operation All of the various parteci the apparatus have been `illustrated in their vnormal or -inoper-ative positions. Assuming that theoperator 'desires .to make a regular application of the tractor and trailer-brakes, he will depress :the brake .pedal I3 in the usual manner. 'The initial lmovement Iof the brake pedal will swing the 4arm :3S and this movement, through -frictional engagement :of the arm 42 with the disc 43, will `close .the switch 455 inthe `manner described Current vwill Vthen -floW from battery .52 through switch .55, Wire 54 and solenoid |51 (Figure 2) and thence back to the battery through grounds |60 and 53. This energizes the solenoid 151i, whereupon the armature 56 Will'move to the vleft as viewed in Figure 2 and the valve 149 will leave the seat H35 and engage the seat |45. Thus the chamber |44 will be disconnected iromthe atmosphere and connected to the vacuum reservoir to `exhaust air `from the motor chamber `|2l (Figure 3) through pipe |.4|. This operation obviously lenergizes the `auxiliary motor and the diaphragm i223 thereof will move upwardly to effect similar movement of the While-tree i |4.

The operation referred to will transmit movement to the rods 82 of the `main motors 15 and will rock both .levers S6. In this connection, it will be noted that the ends of the Whittie-tree contact the collars rilei and thus the vrods 82 will be moved vertically :and these rods will rock the cranks .86 inthe same manner as'when the main motors 15 .are yenergized in the manner to be described. Thus a single auxiliary motor will .be energized upon initial 4'movement of the brake pedal from its normal position to apply the trailer brakes.

This application of the trailer brakes, of course, will take place to a limited 4exten-t to provide a substantial snubbing-of -such brakes. oviously asingle auxiliary motor 12e oi the typeillustrated cannot perform the functions of the two 'main motor '15 to apply the brakes to the same extent as will be done when the main motors are energized, Such full trailer 4brake application is not desired, and the fuller application of these brakes will take place later when the `motors 15 yare energized. Whereas the vacuum 'in the tank inthe reservoir e@ corresponds to .the maximum Avacuum in the intake manifold (21, vthe `pressure regulating valve *.54 provides a less degree of vacuum in the reservoir i5 ,this vacurunpreferably being approximately corresponding :to 7 inches of mercury.

simultaneously with application of Accordingly, application of 4-:the brakes through the auxiliary motor '|20 will voccur to less than half the extent which is possible through .maximum energization-of .themotors 15.

Particular attention is invited .to the fact `that .the trailer brakes by energization of the motor |26, the da phragrns 1-8 of the motors 15 will be moved -upwardly by the motor rods 82. This .operation takes place instantaneously upon Yinitial:operation of the lbra-ke pedal through energizailion` of the solenoid |51; The valve seats |45 .and l|46arefof relatively great diameter, thus resulting in extremely rapid evacuation fof the auxiliary motor chamber |24. Thisfoperation is completed prior `to the connection of the pipes 13 :to the'lvacuum reservoir 6|) .and While the Vpipes 13 are Astill connected to the atmosphere. When the diaphragms 18 are moved 'upwardly in fthe marmer described, air will be rapidly displaced from the variable ypressure chambers of the main trailer brake motors 15. The pipes 13 .being1in1communication with the atmosphere. such displaced air could flow through fthe 'pipes 1x3 for discharge to the atmosphere andthe system is fully .operative in this manner without the `use `of -the ball check valves H33. -Due to line friction, etc., the exhausting of the displaced .air through pipes 13 is somewhat restricted .and it is for this 'reason that the ball .checkvalves |03 are preferably employed. These balls .are very lightly .held on their seats bythe springs |66 Yand accordingly air displaced from the :motor chambers 55 is .relatively freelyexhausted.

In this connection itis pointed out that most of the movement of the parts as .describedtakes place to move the brake shoes of .the trailer into engagement with the drums. Thereafter, very little .movement ofthe partsis required-since the cranks 86 will move only very slightly after 4the brake shoes have engaged with ythe drums to build up watever degree of braking .force is desired. The operation ofthe auxiliary .motor |25, therefore, mechanically moves the diaphragme 18 of the motors 15 substantially to their limits of movement.

The various operations .described .above take place substantially instantaneously upon initial movement .of the brake pedal |3. After the switch 5|) is closed, the arm 42 can partake .of .no further movement, ,and the .disc V40 will .rotate relative to the portion of .the arm 42 in .contact therewith during the remaining .movementof the brake pedal I3. Such movement displaces fluid from the master cylinder into .the .low pressure cylinder 3|) .of the booster mechanism v| 5. .In accordance with the disclosure .of the vKlim kiewicz patent referred to, .the booster mechanism will be operated to generate braking pressures .in the tractor wheel cylinders `34 vproportionate to the extent of operation vof the brake pedal I3. Fluid flow-ing into the low -pressure cylinder 35 energizes the booster motor i8 -by operating the control `valve mechanism therefor as disclosed in .the .Klimkiewicz patent. The chambers 22 and 23, which arenormally vin toommunication with each other, and with -the intake maniold through pipes 25 tand 26, will be fdisconnected from eachother and air will be sup' plied to the chamber 23. The lincreased pressure occurring .in the chamber '23 will move the pressure-responsive unit of the booster .motor #|78 and accordingly the .desired braking pressure'wvill be supplied to the Wheel cylinders34.

The increased :pressures occurringn'the chamber 23 lwill becommunicated through pipe 55 to the relay mechanism 'I0 in the usual manner. This requires an appreciable length of time due to the length of the pipe 55 and the line friction occurring therein. It is during this interval of time that the auxiliary motor I 20 functions in the manner described above.

As soon as the pressure rise in the pipe 55 occurs to the extent upon which the relay mechanism 'I0 depends for its operation, the pipes 'I3 will be disconnected from the atmosphere and connected to the reservoir 60 in accordance with the conventional operation of the relay 'valve mechanism. The connection of the pipes 'I3 to the vacuum reservoir 60 will result in the evacuation of the chambers 95 of the main trailer brake motors 15. As previously stated, the-diaphragms 18 of these motors will have been moved upwardly substantially to their limits of movement during which most of the air will have been displaced from the chambers 95. When the pipes 'I3 are connected to the reservoir 60, therefore, it is unnecessary to move any great volume of air out of the chambers 95 and the pressures in these chambers will drop very rapidly to establish vacuum in these chambers to an extent proportional to energization of the booster motor I8. Thus the trailer brakes will be properly applied in accordance with the operation of the brake pedal I3 and substantially in proportion to the degree of energization of the booster motor I 8.

From the foregoing it will be apparent that the present system functions to positively provide for trailer brake application ahead of tractor brake application, thus preventing dangerous jack-knifing through which serious accidents have occurred in tractor-trailer combinations. Full trailer brake application will not occur by energization of the auxiliary motor |20, but the brakes will be applied to an ample extent to prevent jack-kning prior to energization of the main trailer brake motors 15. These motors will be energized more rapidly than is true of conventional systems because ot the substantial reduction in the time necessary for evacuating the motor chambers 95 for the reasons stated.

It is the common practice among drivers of tractor-trailer combinations to use the hand valve referred to when it is desired to provide a brake snubbing operation, for example when slowly decelerating vehicle speed or when going down an incline. The same operation may be readily performed with the present system. If such operation is desired, it merely is necessary for the operator to slightly depress the pedal I3 to close the switch 50 -without materially displacing hydraulic fluid from the master cylinder I0. Under such conditions, the booster mechanism I5 will remain inoperative, but the auxiliary trailer brake motor I20 will be energized in the manner described above. i

As previously stated, the switch 50 may be operated by or independently of the brake pedal I3. When the switch is operated by the brake pedal I3 it not only is highly desirable to close the switch upon initial brake pedal operation but also to open the switch upon the initial releasing movement of the brake pedal. This is accomplished in the present instance through frictional engagement of the arm 42 with the disc 40. After a substantial brake application, initial releasing movement of the brake pedal I3 will turn the disc 40 in a clockwise direction and this disc will frictionally move the arm 42 to release the switch 50 and de-energize the solenoid |57, The

Cir

. 1l)A valve I 49 accordingly returns to its normal position shown in Figure 2 as the result of initial releasing operation of the brake pedal. In this way, the auxiliary motor I 20 is de-energized as quickly as it was previously energized, thus permitting the full releasing of all of the brakes without any dragging of the trailer brakes as would occur if the switch 50 were not opened until the brake pedal I3 has returned almost to its completely released position. This particular switch mechanism is disclosed and claimed in the copending application of Jeannot G. Ingres, Serial No..

656,363, referred to above.

The two main motors 'I5 are shown in Figure 3 in the approximate relative positions they occupy in most trailer installations. The use of the auxiliary motor I 20 in conjunction therewith does not disturb such normal relation of parts. The auxiliary motor constitutes an auxiliary installed as an addition to the conventional systems, and the parts of the apparatus i'lt and operate perfectly in conjunction with such auxiliary systems. f

We claim:

1. A vehicle braking mechanism comprising a plurality of diilerentia1 pressure operated motors each having mechanical connections for operating one of the brakes of the vehicle, means'for simultaneously energizing said motors, a single diiTerential uid pressure operated motor having connection with said mechanical connections to simultaneously apply the vehicle brakes, means for energizing said single motor independently o i` energization of said plurality of motors, and means having a single manually operable element for controlling both of said motor-energizing means, said element having a normal inoperative position from which it is movable to rst operate the motor-energizing means of said single motor and then operate said iirst named motor-energizing means simultaneously with the operation of the motor-energizing means of said single motor. p

2. A vehicle braking mechanism comprising ,a

plurality of differential fluid pressure operated f motors each having a mechanical connection for operating one of the vehicle brakes, a single differential uid pressure operated motor, lever means connecting said single motor to said mechanica-l connections to simultaneously operate them and apply the brakes independently of energization of said plurality of motors, a pair of control valve mechanisms one for said plurality of motors and the other for said single motor, and means comprising a single manually operable element movable from a normal position and effective upon such movement for I'lrst operating the control valve mechanism for said single motor and then both of said control valve mechanisms.

3. A vehicle brake operating mechanism comprising a pair of differential fluid pressure operated motors each `having a pressure responsive unit therein, Amotion transmitting means for connecting each pressure responsive unit to a -vehicle brake for operating it, each motor of said pair having a constant pressure chamber, and a variable pressure chamber normally open to the atmosphere, valve means operable for connecting said variable pressure chambers to a source of partial vacuum, and a single dierential uid pressure operated motor connected to both of said motion transmitting means and energizable for simultaneously operating them to apply the brakes and to move said pressure responsive units attractie:

rr to displace air` from` variable pressure cham bers.

s. AA vehicle l brake operating mechanism. com-- prising a pair of; diierenti'al ituid pressurey operatedl motors: each having: a pressure responsiveV unit therein, motion transmittingv means ioroon.-` necting eachpressure responsivei unit to ai vehicle: brake: for operating it, each motor of. said* pair, having a constant pressure. chambenanda variv able pressure` chamber: normally open to theA atmosphere, valve meansl operable iorconnecting. said variable pressure chambers to:- a; sourcef of partial vacuum, a single. diierential' fluid?V pres- Sure operatedmotor having a pressure responsive unit therein, levernieans connecting: thepressure` responsive unit oiV said single motor; to; both of.' said'. motion transmitting means to simultaneously operate the. latter to apply,y the. braises' and tc.- movei the.. pressure: responsive' units of themetors or; said? pairf to displace ain from said vari--v ableppressure chambers, and; means for establishf. ing differential pressuresin saidl single motor' dependently of the connection of said variable pressure chambers to the source of vacuum..

` 5.` A. vehicle brakeoper-atingmechanism comprising. apair of dierentiab uid pressureoperatedv motors each` having. a pressure, responsive unit .therein,. motiontransmitt-ing meansfor con necting eachY pressure. responsive unit. to avehicle brake for operating` it, each motor of: said pair having a.I constant.Y pressure chamber, ancla.` vari.- able pressure chamber normallyopen to. the. at.- mosphere, valvel means operableior. connectingsaid, variable pressure chambers to a source. ofv partial-vacuum, a. single, diilerential iiuid pres,- sureoperated. motor, having a pressureV responsive unitthereim lever means connecting thepressure responsiver unit., or. said single motor. to.- both of. saidr motionr transmitting meansI to simultaneously operates the latter. to .apply the. brakes. and temo-vethe. pressure, responsive units ci the. mo,- tors of/said pair. todisplaceair from. saidv variable. pressure chambers, control means operable for establishing, dierential Vpressures infsai'd single moton andaA control mechanism comprising, a. singlemanually operableelementior -rstoperat.- ingsaidV controlmeans to energize said singlemotor and then operate said control'means andsaid' valve means to maintain. energiaation of' said single motor and to connect saidvariable pressure chambers to the source of vacuum.

. 6. A vehicle brake operating mechanism comprising a pair of differential iiuid pressureoperatedv motors each having a pressure responsive unit therein, motion transmitting means for connecting each pressure responsive unit to a vehicle brake. for operating it, each motor of said pair having a consta-nt` pressure chamber, and a variable pressure chamber normally open to theV atmosphere, valve means operable for connecting said variableI pressure chambers to a source of partialvacuum, a whiffle-tree lever pivotallyl con-- nectedVv at its ends to said motion transmitting means, a single diierentia-l''uid pressure operated motor having' a pressure responsivel unit connected to said lever intermediate the ends thereof, and control valve means for establishing diierental pressures in said'singl'e motor tobodily movesaid lever and simultaneously operate sai'd motion transmitting connections toapply the brakes and to movee the pressure responsive units of-y the.motors1.of'said pair to displace:v air therefrom. independently of the connection. of said variable pressure; chambers to said source of vacuum..

'Til A. vehicle brake. operating: mechanism com-i prisinga a pair of; diierentials, fluid: pressurel opl erated motors. each having a` pressure responsive unit'therein, motionitransmitting means. for connecting eachr pressure responsive unitI to a vehi4 cle brake. for operating; it, each motor of said pair having a constant pressure chamber, anda-variable-pressure chamber' normally open to the. atmosphere, valve means operable for connecting' saidvariable pressure chambers to a source of partial. vacuum, a Whiiiie-tree lever pivotallyconnected` atV its encl's-V to said` motion transmitting means, a single auxiliary iiuid.` pressure motor havingia pressureY movable unit connectedlto said leverintermediate. the ends thereof; saidl single motor having a constant pressure chamber and a .vari'ala'le-pressureV chamber, aT control valvel nor mall'y connecting' the variable pressure chamber of said single motorY toA the atmosphere, and

l meansrf'or operating'said valve to disconnectthe variable pressure chamber or said single motor from the atmosphere and' connect it' to a source of vacuum tof energize said; single motor.

8". Apparatus constructedr in accordance with claim 7' provided with a mechanism for control# ling said Vvalve: means and saidt control valve andv comprising a single manually operable element having a normal position from which it is movable to -rstl operate said control valve andthen operate said controllval've andfsaid Valve means.

9. A vehicle brakeloperating" mechanism com'- prising a pair of dilerential" fluidpressuref operated motors each having' a pressureI responsive member therein, a rodl'connected'to each pressure responsive member; each motor having a constant pressure chamber and a variable pressure' chamber normally open to the atmosphere', each-'of said' rods having' mechanical. connection with a vehicle brake to@ operatez it, valve means operable for connecting said variable pressure chambers to a source of'partial vacuum', a whifiie-tree lever' pivotally connected at its ends to said rods, a single differential fluid; pressureop-A erated motor having apressu-re responsive unit connected to said' lever inter-mediate itsencls, and' a control valvefor estabiishing differential pressures in said single motor to bodily move said leve-rand simultaneously'operatesaid rods to ap'- ply thebrakes and to move the pressure responsive members of saidpair` of motors to displace airtherefroml independently ofthey connection of said variable pressure chambers to said source of vacuum.

101 Apparatus constructed in accordance with claim 9provided with a mechanism comprising a pedal having a normal position from which it is movable to first operate saidI control valve and then simultaneously operate said control valve and said valve means,

ll'. A brake operating mechanism fora tractortrailer combination wherein the tractor and trai-ler are each provided with brake operatingmeans. a booster mechanism on the tractor comprising a fluid pressure operated booster motor for operating the tractor brake operatingmeanaa pair ofr fluid pressure motors on the' trailer each having a pressure responsive member therein, motion transmitting means connecting each pressureresponsivemember to az trailer brake operating means, each motor of saidv pair having a constant pressure chamber andI a vari'aole'pressure chamber normally open` to the atmosphere', asource of'vacuum for the motors of' saidI pair, conversion valvemeans on the` trailer remote from said booster motor responsive to energization of saidv booster motor to control connection of said variable pressure chambers to said source, a single motor energizable for applying the trailer brakes and to move said pressure responsive members to displace air from said variable pressure cham- 5 bers, and common manually operable means for energizing said booster motor and said single motor, said common means comprising a manually operable element having a normal position from which it is movable and a mechanism operable by said element throughout movement thereof from its normal position for energizing said single motor, there being a time lag in the energization of said pair of motors due to the remote position of said conversion valve mechanism from said booster motor whereby said single motor Will be energized prior to energization of said pair of motors.

JEANNOT G. INGRES.

EDWARD G. HILL.

The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Number Name Date Livingston Nov. 22, 1927 Cady Sept. 22, 1931 Kerr Mar. 23, 1937 Leupold Jan. 2, 1940 Stehlin May 14, 1940 Winn Feb. 25, 1941 Keith Dec. 19, 1944 FOREIGN PATENTS Country Date Italy Nov. 26, 1930 

